What to Do the Aquarium’s Heater Light is Flickering?

Heaters are crucial components for preserving the tank’s atmosphere and water temperature, as well as the health of the fish.

You can keep the water heated as needed by using the light to determine if your heater is functioning properly or not.

In reality, there are several causes for the heater’s strange behaviour. The improper setting, a broken heater, or simply a poor power supply from the filter might result in severe harm.

You might not first think this issue matters, but it does. If you don’t solve this problem, it can harm the aquarium’s essential parts. Doing so might cost you a lot.

I’ll describe the reasons for this heater flickering problem and how you may quickly determine the source. In addition, I’ll explain how to avoid this issue from arising in the first place.

To learn more about the aquarium heater light flickering problem, keep reading.

Why Does the Aquarium Heater Light Flickering Happen?

The blinking of the heater light is occasionally natural and poses no risk mostly. You may frequently see these lights flicker, which can make you concerned about your fish.

Since this issue might occur at any time for a myriad of factors, keep a close check on every piece of equipment in your tank.

There are several reasons why the heater may flicker, among them:

  1. Thermostat Issue: The thermostat essentially controls how much heat a heater generates.
    When the thermostat is unable to determine the heater’s actual temperature, it may blink to indicate a temperature imbalance.

  2. Electricity Flowing Through the Filter: The heater flickers when the current generated by the filter runs through the water. The flickering is a sign of an odd passing stream.

  3. Rapid Cycles: The heater’s unusual heating patterns might occasionally accelerate. In this instance, the heater begins to flash to signal an abnormal situation.

  4. Inadequate Power Supply: There are instances when the equipment’s power supply drops and current fluctuations rise, causing it to work abruptly and start flashing.

    In this situation, the heater starts to flicker to show that the power supply is insufficient.

  5. Malfunctioning Heater: You will experience troubles with the heater’s low cost and poor quality. The heater may begin flashing as a warning before it stops functioning entirely.

    The heater is essentially being warned that it is not getting or generating enough heat.

You should carefully read the aquarium heater’s instructions to identify the causes of the flickering.

How Do You Fix a Flickering Issue of an Aquarium Heater?

If you notice that the aquarium heater’s indicator light is constantly flashing, it is advisable to find the problem as immediately as you can and fix it.

These instructions can help you to resolve your aquarium heater light flickering problem:

  • Verify whether your heater is receiving a sufficient power supply. Do not leave the aquarium on for a long period. It can result in the heater receiving inadequate electricity.
  • If the heater’s flickering is being caused by the current that is running through the water. Then deactivate the filter first to determine whether it is the cause or not.
  • If this is the cause of the problem, then reduce the flow rate a little. It will fix the heater’s flickering problem.
  • Take proper care of the filter and keep it maintained, and make sure you get a high-quality one before you buy.
  • Place the thermostat carefully by following the installation manual. Place a submersible one away from the wall or bottom and allow it to fully submerge in water.
  • To prevent any mishaps, ensure that the heater you purchase is of good quality because longevity is dependent on quality. Perform a thorough analysis of the heater’s quality and durability before making a purchase.

Is the Blinking of the Aquarium Heater Normal?

The flickering of the heater is usually normal. The light can blink when it experiences a slight change in the current flow sometime.

The heater turns on when the light blinks on and turns off when the light goes out. That is acceptable since it has an internal thermostat that shuts itself off when the temperature is reached.

It’s usual for the flickering problem to last for several days. In this situation, temporarily turn off the switch and wait.

Blinking over a few days is therefore not a major concern, but if it persists for a while, you have to find the source and prevent it.

Does My Aquarium Heater’s Red Light Indicate Any Problem?

Numerous aquarium heaters come preinstalled with red lights; while they appear threatening, they are not.

The fact that it is still heating and has not attained the appropriate temperature is shown by the red lights. Let it carry out its task without worrying.

The low voltage thermostat keeps the water at 25.5 degrees Celsius without the need for any adjustments. Make sure to choose the right heater for the size of your tank. A heater that is too small for your tank may result in underheating.

Where To Place The Heater of the Aquarium for Uniform Heating and Prevent Flickering?

To guarantee uniform heating, place your heater next to a filter intake or outlet or a circulation pump. The heater will blink if there is an imbalance in the heat distribution, which might harm the heater.

For maximum results, submersible aquarium heaters can be placed horizontally close to the tank’s bottom. If you wish, you may also place them vertically.


Making sure to resolve the aquarium heater light flickering problem is not difficult. Regular inspection of the heater’s flickering helps prevent more harm because this flashing is a type of warning as well.

Now that you are aware of the cause of the heater flickering, you can quickly remedy it. Before purchasing any parts, it is best to check with a specialist and replace any damaged components.

Please adhere to my directions precisely if you want a wise solution and to prevent any problems with the heater’s unusual behavior.

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Arif H Fahim

Welcome to PetFishTank! My name is Arif. I make an effort to publish educational articles using my many years of expertise as a fish owner.

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